Hand-me-down Speech

No one really knows where human language comes from. One possibility is that language evolved from the hand gestures of our ape and hominid ancestors and not from their vocalizations. The view promoted by Michael Corballis in From Hand to Mouth is that our ancestors used both vocalizations and hand gestures to communicate, but that—particularly after the evolution of bipedalism and an increase in brain size—gestural communication became more complex and acquired the characteristics of a language, including symbolic referents, grammar and a syntax. Eventually there was a shift from gestures to speech as the main medium for expression.

One of the first to propose the gestural theory of language origins was the 18th-century French philosopher Abbé Étienne Bonnot de Condillac; it was then resurrected by the American anthropologist Gordon W. Hewes in the 1970s. Corballis expands the theory and integrates many research findings from disciplines such as paleoanthropology, primatology, linguistics, developmental psychology and neuroscience.

He does a good job: From Hand to Mouth is informative and entertaining. It shows that many serious scholars are involved in research on human evolution and language origins—and also that there is a great deal of wackiness. Take, for example, the proposal by Julian Jaynes that until about 3,000 years ago, human behavior was guided by hallucinations generated by a "bicameral" brain, which were interpreted as the voices of "the Gods." According to Jaynes, some floods and earthquakes in the second millennium b.c. caused the brain to become lateralized, leading to the emergence of self-consciousness and individual responsibility for action, mediated by the left hemisphere. As a result, people no longer waited for the Gods to tell them what to do but started making their own decisions.

Corballis makes his own small contribution to the wackiness sometimes found in the field of paleoanthropology by suggesting that human bipedalism may have evolved as an adaptation to wading through water, or perhaps to swimming. If he is right, one may wonder why the wildebeest of the Serengeti do not walk bipedally and why humans did not evolve fins, too.

Some readers of From Hand to Mouth may have difficulty discerning the boundary between facts and fiction in the book. The problem is that much of the research discussed by Corballis has little or no relevance to the theory that language evolved from gestures and indeed could just as easily be interpreted as supporting other theories of language origins. He cites work that appears to be consistent with the gestural theory, but, unfortunately, he gets some of the facts wrong.

For example, in his eagerness to prove that nonhuman primate gestures are more languagelike than are vocalizations, he provides a caricature of primate vocalizations as being strongly linked to emotional states; lacking voluntary control or external referents; not being directed to specific individuals but to the community at large; and being just fixed responses to fixed situations. Just as vocalizations are unfairly downplayed, the languagelike nature of primate gestures is grossly exaggerated. For example, there is little or no evidence to support Corballis's claims that the spontaneous gestures used by chimpanzees or other apes are iconic, that they refer to actions rather than objects, that they are learned by emulation, or that they "emerge from actions on the physical world" and then become conventionalized (this last is a suggestion of Frans de Waal). Corballis also goes too far when he states that "it is becoming clear that [apes] use communicative gestures in the wild, often in one-on-one situations that somewhat resemble human conversational language."

Corballis fails to mention that the great apes are unique among nonhuman primates in their use of hand gestures for purposes of social communication. Moreover, although there is no reason to believe that the vocalizations of the great apes are any more complex than those of other animals, their repertoire of nonvocal signals and their flexibility in using those signals are probably greater than in other species. Although this constitutes no evidence that human language has any relation whatsoever to ape gestures, it raises interesting evolutionary issues about the selective pressures that promoted the use of gestural communication in the great apes. Comparative behavioral research addressing these issues may not tell us anything new about the origins of language but could help us understand the social and ecological changes driving the evolution of primate communication.

Much less research has been done on gestures in human and nonhuman primates than on vocal and verbal communication. Whether or not Corballis's view of language origins is correct, From Hand to Mouth will raise awareness about the importance of gestures and the crucial role they play in communicative interactions.--Dario Maestripieri, Human Development and Evolutionary Biology, University of Chicago